An, T.-Q. | Search bioRxiv

bioRxiv2024

Identification of a Conserved B-Cell Epitope on the Capsid Protein of Porcine Circovirus Type 4

Porcine circovirus type 4 (PCV4), a recently identified circovirus, is prevalent in numerous provinces in China, as well as in South Korea, Thailand, and Europe. PCV4 virus rescued from an infectious clone showed pathogenicity, suggesting the economic impact of PCV4. However, there remains a lack of understanding regarding the immunogenicity and epitopes of PCV4. This study generated a monoclonal antibody (MAb) 1D8 by immunizing mice with PCV4 virus-like particles (VLPs). Subsequently, the epitope recognized by the MAb 1D8 was identified by truncated protein expression and alanine scanning mutagenesis analysis. Results showed that the 225PKQG228 located at the C-terminus of the PCV4 Cap protein is the minimal motif binding to the MAb. Homology modeling analysis and immunoelectron microscopy revealed that the epitope extends beyond the outer surface of the PCV4 VLP. Moreover, the epitope is highly conserved among PCV4 strains and does not react with other PCVs. Together, the MAb 1D8 recognized epitope shows potential for detecting PCV4. These findings significantly contribute to the design of antigens for PCV4 detection and control strategies. IMPORTANCEPorcine circovirus type 4 (PCV4) is a novel circovirus. Although PCV4 has been identified in several countries, including China, Korea, Thailand, and Spain, no vaccine is available. Given the potential pathogenic effects of PCV4 on pigs, PCV4 could threaten the global pig farming industry, highlighting the urgency for further investigation. Thus, epitopes of PCV4 remain to be determined. Our finding of a conserved epitope significantly advances vaccine development and pathogen detection.

microbiology↗

bioRxiv2023

Inflammation plays a critical role in damage to the bronchiolar epithelium induced by Trueperella pyogenes in vitro and in vivo

Trueperella pyogenes can cause severe pulmonary disease in swine, but the mechanism of pathogenesis is not well defined. T. pyogenes-induced damage to porcine bronchial epithelial cells (PBECs), porcine precision-cut lung slices (PCLS) and respiratory epithelium of mice remains unknown. In this study, we used T. pyogenes 20121 to infect PBECs in air-liquid interface conditions and porcine PCLS. T. pyogenes could adhere to, colonize and induce cytotoxic effect on PBECs and the luminal surface of bronchi in PCLS, which damaged the bronchiolar epithelium. Moreover, bronchiolar epithelial cells showed extensive degeneration in infected mice lungs. Furthermore, western blot showed the NOD-like receptor (NLR)/ C-terminal caspase recruitment domain (ASC)/caspase-1 axis and nuclear factor-kappa B (NF-{kappa}B) pathway were involved in inflammation in PCLS and lungs of mice, which also confirms PCLS provide a platform to analyze pulmonary immune response. Meanwhile, the levels of p-c-Jun N-terminal kinase (JNK), p-extracellular signal-regulated kinase (ERK) and p-protein kinase B (AKT) were increased significantly, which indicated the mitogen-activated protein kinase (MAPK) and Akt pathways were also involved of inflammation in T. pyogenes-infected mice. In addition, we used T. pyogenes 20121 to infect tumour necrosis factor alpha (TNF-)-/- mice, the results indicated apoptosis and injury in respiratory epithelium of infected TNF--/- mice were alleviated. Thus, pro-inflammatory cytokine TNF- played a role in apoptosis and respiratory epithelium injury of mice lungs. Collectively, our study provides an insight into the inflammatory injury induced by T. pyogenes, and suggests that blocking NLR or TNF- may be a potential therapeutic strategy against T. pyogenes infection.

immunology↗